PVC Collars

Collars manufactured from PVC are also available, for installation as part of a full PVC waterproofing membrane systems. They are fitted around the outside of the pipework which emerges from the top of the concrete deck, things such as foul air vents and stand pipes. Obviously it is important that the small cavity between the cast concrete and the HDPE pipe emitting form the hole is fully sealed, which is why collars are fitted over the whole area and bonded to the waterproofing membrane.
http://www.wallbarn.com/products/roof-outlets-vents/roof-outlets-collars/pvc/pvc-collars/